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United States Patent | 6,034,568 |
Bonaccio ,   et al. | March 7, 2000 |
An operational amplifier with two differential input stages is used to separately achieve low offset voltage and broad bandwidth characteristics. One input stage addresses dc and low frequency signals while the other addresses broadband frequencies. All transistors forming the dc stage are biased in the sub-threshold region. Following the two differential input stages, the signal paths are recombined in a capacitive cross-over network that provides outputs for subsequent amplification. The cross over frequency is adjustable from 15 kHz to 50 kHz using small practical values for the cross-over capacitor. The gain balance between the two input stages is adjustable by resistors and/or predetermined width/length ratios of the operational amplifier transistors.
Inventors: | Bonaccio; Anthony R. (Shelburne, VT); Michail; Michel S. (Poughkeepsie, NY); Pricer; W. David (Charlotte, VT) |
Assignee: | International Business Machines Corporation (Armonk, NY) |
Appl. No.: | 097484 |
Filed: | June 15, 1998 |
Current U.S. Class: | 330/253; 330/295 |
Intern'l Class: | H03F 003/45 |
Field of Search: | 330/9,253,295,302 327/307 |
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